[clang] [llvm] [X86] Enhance kCFI type IDs with a 3-bit arity indicator. (PR #117121)

[Alice Ryhl via cfe-commits]

Darksonn wrote:

Sami, I'm guessing you're mainly talking about rustc and clang needing to use llvm versions that agree on the kCFI implementation in use? Or are there additional things we need to do to make Rust support it / some fundamental reason this approach can't work in Rust?

Either way, it would be nice to have some way to set the hashing method being used, or at least, a way to query which hashing strategy is used. We are going to want logic in Kconfig to ensure that rustc and clang use the same strategy, or at least a way to detect when they don't so we can fail the build with a good error message.

cc @maurer 

https://github.com/llvm/llvm-project/pull/117121